External Casing Packer

ABSTRACT

A method and apparatus for cementing a zone of borehole casing using an external casing packer (ECP). The method involves sealing the base of the ECP with a ball dropped in a seat, and then pressurising the casing to inflate an elastomeric packer sleeve through a one-way valve. When a design differential pressure is reached across the casing and elastomeric sleeve, a grout valve in the upper part of the packer opens to limit the sleeve inflation pressure and to provide a one-way valve through which cement grout passes to permit grouting of the annulus between the casing and the borehole.

RELATED PATENT APPLICATION

This PCT application claims the benefit of two Australian provisionalapplications, both filed on 19 Nov. 2009, and accorded respectiveapplication numbers 2009905659 and 2009905660. The disclosures of theAustralian provisional patent applications are incorporated herein byreference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates in general to the field of completinghydrocarbon or water wells, and more particularly to methods andapparatus for manufacturing inflatable packers, and sealing the base ofa casing by cement grouting the annulus above the packer, while notdamaging the underlying borehole with grout.

BACKGROUND OF THE INVENTION

The conventional process to install a casing in a borehole is to firstdrill a borehole, install a casing therein, and cement the casing inplace. The borehole can then be extended beyond the bottom of the casingby drilling a smaller size hole, which usually occurs in the productionzone. The cementing process usually involves pumping cement through thecasing and out of the bottom thereof, and up into the annulus betweenthe casing and the borehole. The cement is displaced downwardly and outof the casing by pumping a drilling fluid or water into the top of thecasing. A cement displacement plug is normally used to separate thewater from the cement in the casing. Sometimes a float shoe (one wayvalve) is attached to the bottom of the casing so as to avoid the needto hold pressure within the casing while the cement in the annulus sets.

An alternative process is to drill the borehole to final gauge anddepth, and then run the casing with an external packer attached in thecasing string or to the end thereof into the borehole. A port at thebase of the external casing packer is closed and the casing ispressurised to set the packer. Cementing ports are then opened above thepacker, cement is pumped through the casing ports and into the annulusto cement the casing in place. At the end of the cementing process adisplacement plug is run down the casing and the cement is displaced outof the casing and into the annulus. The cementing ports are then closed.The casing is then free of cement and the annulus is cemented within theborehole. The normal process is then to run a drill string and drill bitback into the casing to drill out any cement remaining in the packer,drill out the cement displacement plug and the bottom port to clean outthe borehole below the packer. In existing external casing packers, thebottom port is usually blocked by a ball dropped into the casing. Thecementing ports are actuated by either rotating, raising or lowering thecasing or by dropping balls or darts of different sizes into the casingto move sliding annular seals.

SUMMARY OF THE INVENTION

The external casing packer according to the various embodimentsdescribed herein is referred to at times as “ECP.” The operation of theECP is however simpler than existing packer systems. The manufacture isalso simpler and more cost effective than other packer devices currentlyavailable.

The external casing packer, according to the invention, is attached tothe outer cylindrical surface of the casing, with the casing extendingabove and in some cases below the ECP. A non-return valve is fitted inthe base of the ECP, which permits fluid to enter the casing from theborehole during lowering of the casing into the borehole, but preventsthe reverse flow of liquids from the casing down into the borehole. Inits simplest form, the non-return valve is a port formed or installed inthe base of the ECP, and is sealed by a ball that is dropped into thecasing from surface. The ball seats in the port in a conventional mannerin the base of the ECP. Such a system enables flow in and out of thecasing until the ball is dropped. Alternative non-return valvearrangements may be used, such as a wire line retrievable plug, or aone-way valve such as a float shoe.

Once the one-way valve in the base of the ECP is actuated, the casing ispressurised to inflate an elastomeric sleeve of the ECP. The inflationof the sleeve is achieved by use of a non-return inflation valve systemlocated between the casing and the ECP sleeve. As the pressure in thecasing is raised, an elastomeric sleeve of the ECP inflates to expandand engage the annular wall of the borehole. At a preset pressure in thecasing, frangible grout valves constructed within the mandrel of the ECPare actuated to open and to subsequently allow a cement grout mixture tobe pumped through the grout valves to the portion of the annulus locatedabove the ECP. The grout valves are constructed to function as acombination of a burst or shear disk, and a non-return check valve. Withthe failure of the burst or shear disk in the grout valve during thesleeve inflation process, the pressure inside the casing drops so thatthe ECP sleeve no longer inflates through the non-return inflationvalve, as the pressure in the ECP sleeve exceeds that in the casing. Thefracturing and the opening of the grout valves thus functions as arelief valve to prevent over-inflation of the elastomeric sleeve. Thus,the preset pressure to which the casing is pressurised is relative tothe point at which the frangible grout valve discs break, and to thedesired pressure to be maintained in the elastomeric sleeve.

At this stage of the process, the inflation valve is closed and thegrout valve of the ECP is activated and opened, whereupon a cement groutmixture is pumped down through the casing. The cement grout mixtureflows down the casing and pushes the grout valves open. The cement groutthen flows through the grout valves and into the annulus between thecasing and the wall of the borehole, in the annulus area above the ECP.When the required volume of cement grout has been pumped down thecasing, a cement displacement plug is introduced into the top of thecasing. A liquid is then pumped down the casing to force thedisplacement plug downwards to the ECP. This is continued until thedisplacement plug reaches a location just beyond the grout valves,whereupon further downward movement of the displacement plug is halted,because a hydraulic lock forms between the cement displacement plug andthe closed non-return valve in the base of the ECP. There is generallyno further need to pressurise the casing to support the cement grout, asthe grout valves are one-way check valve devices which prevent thebackflow of cement grout from the annulus back into the casing. Thegrout valves also permit breaks or interruptions in the cement groutpumping process without the backflow of the grout from the annulus backinto the casing. At the completion of the cementing operation a drillstring can be run into the casing to drill out the cement displacementplug and the bottom non-return valve arrangement, along with anyresidual cement grout which has hardened in the drill path.

Various features of the invention include the grout valves, theinflation valves and the manufacture process which can be incorporatedinto a single elastomer layer bonding operation.

The one-way grout valves each comprise a chamfered valve member which ispreferably a seal disc that scats in a chamfered port formed in the ECPmandrel above the packer sleeve. The valve or seal members are attachedto respective burst or shear discs. The discs are preferably constructedof a frangible material having a well defined shear failure stress suchas some plastics, metals or ceramics. The chamfered valve member isattached to an elastomeric grout valve sleeve which surrounds themandrel. In the absence of pressure in the casing, the elastomericnature of the grout valve sleeve retains the chamfered valve member andensures a seal with the chamfered seat of the mandrel on closure.Preferably, the elastomeric grout valve sleeve is bonded to the top ofthe chamfered valve member and forms part of the inflatable ECP sleevesituated around the mandrel.

The inflation valve comprises a flap of an elastomeric material situatedon the inflatable elastomeric sleeve side of the mandrel. The inflationvalves each cover a small port formed in the mandrel. Fluid cantherefore flow through the inflation ports in one direction and displacethe flap outwardly to inflate the elastomeric sleeve of the ECP. Oncessation of the fluid flow to inflate the ECP sleeve (when the groutvalve discs shear and open), the inflation ports are closed by therespective flaps, which prevents the packer sleeve from deflating. Theinflation flap preferably comprises part of the ECP sleeve constructionto simplify the manufacturing process.

The inflation valves and the grout valves are both operated in asequence during the process of inflating the elastomeric sleeve to setthe packer and casing in the borehole. The inflated sleeve provides anobstruction in the borehole annulus so that the annulus area above theobstructing sleeve can be filled with a cement grout mixture. To thatend, the casing and ECP attached thereto arc lowered at the desiredlocation in the borehole. The open one-way valve in the bottom of theECP allows air and any liquid in the lower part of the borehole toequilise during lowering of the casing and ECP therein, as the ball hasnot been dropped down the casing. A ball is then dropped down the casingto seat with the one-way valve in the bottom of the ECP, therebyplugging said valve. The casing is then pressurised with a liquid toinflate the elastomeric sleeve via the inflation valves. As the sleeveis inflated and engages the sidewall of the borehole, the pressure ofthe inflation liquid increases, whereupon the shear point of the groutvalves is reached and such valves arc actuated and opened. When thegrout valves burst open, the inflation valves automatically close due tothe reverse differential pressure across the inflation valves. Theclosed inflation valves leave the sleeve pressurised and compressedagainst the wall of the borehole. The cement grout mixture can then bepumped down the casing and out of the opened grout valves into theannulus area above the inflated sleeve.

The sealing system between the packer sleeve and mandrel comprises thepacker sleeve being bonded directly to the packer mandrel at one end ofthe mandrel. At the other end of the packer there is a seal which movesaxially along the outer surface of the mandrel and accommodatesshortening of the packer sleeve as it expands radially outwardly duringinflation. In most packers this takes the form of a sliding elastomerichydraulic seal between the sleeve and the mandrel. Such a hydraulic sealrequires a substantial housing to contain it. In the preferredembodiment of the invention, the sliding hydraulic seal is replaced by asealing sleeve of elastomer that is bonded at one end to the packersleeve at a position below a packer retaining ring, and to the packermandrel at the other end. Thus, as the packer sleeve is inflated andshortens in a longitudinal direction, the sealing sleeve compresseslongitudinally but maintains a seal to the mandrel. The sealing sleeveis pressed via inflation pressure against the mandrel and is preventedfrom being torn from the packer sleeve by the packer retaining ringwhich maintains an outer diameter and confines the seal. In oneembodiment, the packer sealing sleeve is reinforced by an open meshinterlayer which is placed on the bias to the packer axis to permitlongitudinal changes in sealing sleeve dimension, and to reinforce theelastomeric sleeve against tears by preventing excessive local strain.

The bonded sleeve system is used to transfer load between the packersleeve reinforcement and the packer retaining ring. In a packer wherethe sleeve is reinforced with flexible cords or straps of lowinextensibility, the reinforcing carries tensile load. The tensile loadis retained against expansion by the packer retaining ring. The loadingforce on the packer retaining ring comprises the component perpendicularto the retaining ring which is restrained by the packer retaining ringoperating as hoop reinforcement. There is also an axial component whichtends to slide the packer retaining ring axially away from the inflatedportion of the packer sleeve. Thus, the retaining ring tends to bepushed over the packer sleeve reinforcement contained in the elastomericsleeve. By bonding a stiff or rigid sleeve, which is in contact with thepacker retaining ring, to the elastomeric sleeve, which is in turnbonded to the reinforcing, shear is transferred between the packerretaining ring and the reinforcement via the rigid sleeve and theelastomer. The rigid sleeve may advantageously be made in alongitudinally split form to permit the easy assembly and bonding to theunderlying elastomer while relieving the manufacture of close toleranceissues. The sleeve system is therefore of low cost to fabricate andrapidly incorporated into the packer construction.

The overall design of the packer, can therefore include one or morefeatures which are easily incorporated into the manufacture of a packerby layers of elastomer to be cured and bonded, or specifically notbonded together, according to the design. The elastomer may be derivedfrom natural or synthetic sources, and is usually bonded together in aprocess involving pressure and heat. This is known for natural rubbersystems as the process of vulcanisation. It is thus possible, to achievevery strong bonding between layers of elastomer and between theelastomer and the mandrel (especially to steel) by the use of thecorrect surface preparation of the metal.

According to one embodiment of the invention, disclosed is a method ofcement grouting a borehole using an inflatable packer system. The methodincludes placing a casing with an external casing packer attachedthereto at a location in a borehole for cement grouting a portion of theborehole annulus that is located above the external casing packer. Alsoincluded is the inflation of an inflatable elastomeric sleeve of theexternal casing packer to block the annulus of the borehole bypressurising the casing with an inflation fluid, which opens a one-wayinflation valve in the external casing packer and inflates theinflatable sleeve to a preset pressure. The preset pressure isdetermined by a pressure relief valve located between the externalcasing packer and the annulus which opens at the preset pressure andthen becomes a one-way grout valve. A liquefied cement grout mixture ispumped down through the casing via the open one-way grout valve which islocated in the external casing packer above a portion of the inflatedinflatable sleeve. The grout valve is biased to a closed position usingan elastomeric member attached to the packer, whereby when the pressureof the cement grout mixture is reduced in the casing, the elastomericmember causes the grout valve to close and prevent backflow of thecement grout mixture from the annulus back into the casing.

According to another embodiment of the invention, disclosed is a methodof setting an external casing packer in an annulus of a borehole to fixa casing therein. The method includes sealing a base of the packer, andpressurising the packer to inflate an inflatable elastomeric sleevesurrounding a portion of a packer mandrel by passing a pressurised fluidthrough a one-way inflation valve into the inflatable sleeve. Theinflation pressure of the inflatable sleeve is limited by using apressure relief valve in the packer which relieves the pressure in thepacker to the outside of the casing when a design differential pressureis reached. The pressure relief valve is used as a one-way valve topermit a grout material to flow therethrough to the annulus of theborehole. The pressure relief valve is closed to prevent a backflow ofthe grout material from the annulus back into the packer.

According to yet another embodiment of the invention, disclosed is amethod of cement grouting a borehole using an inflatable packer system.The method includes lowering into a borehole a casing with theinflatable packer system attached thereto. The casing is pressurisedwith a fluid so that the pressurised fluid enters one or more one-wayinflation valves in the packer system to inflate a sleeve and obstructan annulus of the borehole. The pressure of the fluid in the casing isincreased until one or more one-way frangible grout valves rupture toallow the pressurised fluid to enter the borehole annulus above thepacker system, whereby the pressure of the casing drops and the one-wayinflation valves close and maintain the sleeve inflated in the boreholeannulus. A cement grout is pumped down the casing and through theruptured one-way grout valves and into the portion of the boreholeannulus located above the packer system.

With regard to yet another embodiment of the invention, disclosed is aninflatable packer system for grouting a borehole annulus. The packersystem includes a mandrel forming a body of the packer system, where themandrel is adapted for attachment to a casing, and the mandrel hasformed therein one or more ports for respective grout valves, and one ormore ports for respective inflation valves. A seat is formed in a bottompart of the mandrel, where the seat is adapted to be blocked by a balldropped down through the casing. An elastomeric sleeve is formed aroundthe mandrel and around the inflation valve ports. An anchor seal isformed at a top portion of the elastomeric sleeve around the mandrelabove the inflation valve ports and below the grout valve ports. Asliding seal is formed at a bottom portion of the elastomeric sleevealong the mandrel. One or more one-way inflation valves are provided,where each one-way inflation valve is located over one of the inflationvalve ports, and each one-way inflation valve is adapted for allowing aninflation fluid to pass through the inflation valve port and into theelastomeric sleeve, but not in the reverse direction. One or moreone-way grout valves are provided, where each one-way grout valve islocated over one of the grout valve ports, and each one-way grout valveis adapted for allowing a cement grout to pass through the grout valveport and into the borehole annulus, but not in the reverse direction.Each one-way grout valve is formed with a frangible member which breaksin response to a predetermined inflation fluid pressure, whereby whenthe elastomeric sleeve is inflated to the predetermined fluid pressurethe frangible members break to enable operation of the one-way groutvalves. The one-way inflation valves then close to allow the elastomericsleeve to maintain the predetermined inflation fluid pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages will become apparent from the followingand more particular descriptions of the preferred and other embodimentsof the invention, as illustrated in the accompanying drawings in whichlike reference characters generally refer to the same parts, functionsor elements throughout the views, and in which:

FIG. 1A-1F schematically illustrate the sequence of steps for installingthe external casing packer in a borehole;

FIG. 2 is a cross-sectional view illustrating the external casing packeraccording to an embodiment of the invention;

FIG. 3 is a cross-sectional view illustrating the grout valve accordingto an embodiment of the invention, in a closed condition;

FIG. 4 is a cross-sectional view of the grout valve of FIG. 3, but in anopen condition;

FIG. 5 illustrates in a one-quarter longitudinal section view the upperend of the packer with the inflation valve, according to an embodimentof the invention, in an open condition; and

FIG. 6 illustrates in a one-quarter longitudinal section view the lowersliding end of the packer and the construction of the scaling sleeveaccording to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1A illustrates the external casing packer, enclosing a casing 2which has been lowered into a borehole 1. The portion of the casing 2above the ECP extends to the surface, and the casing portion 3 below theECP is optionally perforated, as shown. The body of the packer isconstructed using a metal mandrel 5. The ECP includes an inflatablereinforced elastomeric sleeve 4 which encircles the mandrel 5. The groutvalve at the upper end of the casing packer is shown as numeral 6. Thepacker seat 8 of the non-return valve is located in the lower portion ofthe mandrel 5, and is a cone of material, usually concrete. Theinflation valve 7 is adapted for use in inflating the elastomeric sleeve4 to obstruct or otherwise block the annulus of the borehole 1.

FIG. 1B illustrates a cementing system attached to the top end of thecasing 2. The cementing system includes a top casing section 10 whichcontains a cement displacement plug 15 therein. Also included are groutand inflation valves 11 and 13 which are connected to the top casingsection 10. Once the casing 2 is situated at a desired location in theborehole 1, a ball 16 is dropped down through the casing 2 and intocontact with the valve seat 8 to seal the bottom end of the packer. Theelastomeric sleeve 4 of the ECP is then inflated by pumping a fluid intothe top section 10 of the casing 2 via port 14 and valve 13. Thepressurisation of the casing 2 causes the flap of the one-way inflationvalve 7 in the packer mandrel 5 to open and permit the pressurised fluidto enter the space between the mandrel 5 and the packer sleeve 4,thereby inflating and expanding the elastomeric sleeve 4 into contactwith the borehole 1.

FIG. 1C illustrates the elastomeric sleeve 4 of the ECP fully expandedand in contact with the wall of the borehole 1. Eventually, thedifferential of the fluid pressure across the expanded elastomericsleeve 4 exceeds a designed threshold, whereupon the frangible groutvalve 6 is activated to open and initially allow fluid to flow from thecasing 2 into the annulus between casing 2 and borehole 1. As notedabove, when the grout valves 6 open, the pressure in the casing 2 dropsand closes the inflation valves.

FIG. 1D illustrates the process of pumping the cement grout 17 into thecasing top section 10 via port 14 of grout valve 13. The cement grout 17passes down through the casing 2 and out of the opened grout valve 6 tofill that part of the annulus above the packer and between the casing 2and the borehole 1. The cement grout 17 also flows down through themandrel 5 of the ECP, to the ball 16 and closed valve seat 8.

View 1E shows a fluid being pumped into port 12 through inflation valve11 while grout valve 13 is closed. This fluid pushes the cementdisplacement plug 15 down into the casing 2 and into the top of themandrel 5 until the cement displacement plug 15 forms a seal below thegrout valve 6. At this point, a hydraulic lock forms between the cementdisplacement plug 15 and the ball 16 in the valve seat 8.

FIG. 1F illustrates the use of a conventional drill bit 19 attached tothe end of a drill string 18 to drill out the cement grout displacementplug 15 (shown already drilled out), as well as drill out the cementgrout 17 within the remainder of the casing 2, the mandrel 5, and theball 16 and valve seat 8. When drilled in the manner noted, theproduction zone below the packer is coupled to the casing 2 above thepacker.

FIG. 2 illustrates the structural details of the ECP. As noted above, inthe embodiment shown the ECP comprises a mandrel 5 partially covered orencircled with a reinforced elastomeric sleeve 4. The sleeve 4 isconstructed of various layers of material to carry out the functionsdescribed herein. The elastomeric sleeve 4 is multilayered and wouldnormally be constructed of a natural or synthetic rubber. The sleeve 4is bonded to the mandrel 5 at the top of the packer beneath outer rigidsleeve layer 23, but is not bonded to the mandrel 5 over the remainderof sleeve 4 length. Between the packer retaining rings 20 and 21 thepacker sleeve 4 may expand outwardly in response to internal, pressureto form a seal in the annulus of the borehole. The packer retainingrings 20 and 21 are manufactured from high tensile steel and are bondedto the elastomeric sleeve 4, and restrained by upper and lower rigidouter sleeves 22 and 23 which are also bonded to the sleeve 4. The rigidouter sleeves 22 and 23 can be constructed of a rigid material or metal,such as steel. The mandrel 5 is shown with threaded connections at thetop 26 and bottom 27 to permit attachment to casing sections locatedabove and below the packer. The absence of bonding between thereinforced elastomeric sleeve 4 and mandrel 5 at the lower end of thepacker allows the lower end of the sleeve 4 to slide up the mandrel 5 asthe sleeve 4 becomes inflated. It is realised that when the reinforcedelastomeric sleeve 4 is inflated, the natural tendency is for theoverall length to become shortened. The other alternative is for thematerial of the elastomeric sleeve 4 to stretch during inflation, butwith the reinforced construction of the sleeve 4, stretching of thesleeve material is not preferred. The seal between the sleeve 4 and themandrel 5 is described in more detail in below. The lower end of themandrel 5 contains a cone-shaped valve seat 8 which forms a non-returnvalve when the ball 16 is dropped down the casing 2 and rests on theconical-shaped seal 8. The cone-shaped element 8 can be cast in concreteor other suitable materials to lower manufacture cost. The non-returninflation valve 7 and the grout valves 6 described above are alsoillustrated. The grout valves 6 described in more detail below arecovered, by an elastomeric grout valve sleeve 25.

FIG. 3 illustrates the details of the grout valve 6 in a closedposition. As noted above, the grout valve 6 is constructed with achamfered port 30 formed in the sidewall of the mandrel 5. Seated in theport 30 is a chamfered valve member 31 which in its preferred embodimentis made of metal and which is attached to a frangible shear disc 32. Theshear disc 32 is preferably made of a material having a well-definedshear strength such as a plastic, metal or ceramic. The force exerted bythe pressure of fluid in the casing during the sleeve inflating processis sufficient to fully inflate the sleeve, and shortly thereafter shearthe shear disc 32. The shear disc 32 is connected to the valve member 31via a fastener 33, shown as a screw. The elastomeric grout valve sleeve25 encircles the mandrel 5 and is bonded to the outer surface of thegrout valve member 31, but not to that part of the mandrel 5 shown tothe right of the grout valve 6 in the drawing. The elastomeric groutvalve sleeve 25 is, however, bonded to the mandrel 5 at the location tothe left of the grout valve 6.

In operation, when the differential pressure across the grout valve 6exceeds a specified design value during inflation of the elastomericsleeve, the peripheral rim of the frangible burst disc 32 undergoesstress and eventually shears, whereupon the chamfered grout valve member31 is activated and moves out from its seated position to thereby allowfluid to flow through the opened grout valve 6. As will be describedbelow, during inflation of the large elastomeric sleeve through the openinflation valves, a point is reached where the elastomeric sleeve isfully inflated in the annulus and the grout valves 6 then rupture andopen. At this time, the pressure in the casing drops abruptly, whereuponthe inflation valves close. To that end, the opening of the grout valves6 function as a relief valve for the inflation of the elastomericsleeve. When the grout valves 6 are forced open, the elastomeric groutvalve sleeve 25 is forced to expand outwardly, as shown in FIG. 4. Afterthe casing is set by the inflated sleeve, the cement grout can be pumpeddown the casing. The force of the liquefied cement grout on the groutvalves 6 causes them to open and allow flow in the direction of thearrow. Once a specified volume of the cement grout mixture is pumpedthrough the grout valves 6 end into the borehole annulus, the cementgrout pumping operation is halted. The expanded elastomeric grout valvesleeve 25 then contracts, which action returns the chamfered valvemember 31 and the remaining part of the shear disc 32 back into a seatedcondition with the chamfered port 30 of the mandrel 5. Once the groutvalve 6 returns to its seated condition due to the contraction of theelastomeric grout valve sleeve 25 around the mandrel 5, a seal isprovided between the chamfered grout valve member 31 and the chamferedport 30 of the mandrel 5.

FIG. 4 illustrates the grout valve 6 in an open position, as notedabove. The frangible shear disc 32 is shown with its peripheral edgesheared off following its failure at the design inflation pressure ofthe ECP. The elastomeric grout valve sleeve 25 positions the chamferedvalve member 31 during fluid flow, including that of cement grout, sothat when the fluid flow ceases, the chamfered valve member 31 returnsto the seated condition in the chamfered valve port 30. The registrationof the grout valve member 31 and the valve port 30 is achieved bybonding the elastomeric grout valve sleeve 25 to the outer surface ofthe chamfered valve member 31 and to the mandrel 5 at location 34. Theelastomeric grout valve sleeve 25 can be manufactured as part of anextension of the packer sleeve, but this is not a necessity.

FIG. 5 illustrates the upper zone of the packer sleeve 4, the inflationvalve 7, the retaining ring 21 and the bonded elastomeric sleeve 4. Thereinforced elastomeric sleeve 4 is of multi-layered construction,including an outer elastomer layer 40, a reinforcing layer 41, (depictedhere as a single layer for diagrammatic convenience, but could be madeof layers of steel cord or steel strips embedded in the elastomer) andan inner elastomer layer 42. The layered elastomeric sleeve 4 is bondedover surface area 43 to the outer cylindrical surface of the mandrel 5.The outer elastomer layer 40 of the reinforced sleeve 4 is bonded to therigid outer sleeve 23 which bears against the packer retaining ring 21at location 44. The retaining ring 21 has acting on it the loads fromthe sleeve reinforcing layer 41. This would tend to move the retainingring 21 axially to the right in the drawing. The rigid outer sleeve 23however restrains the retaining ring 21 from being moved to the rightbecause it is bonded to the elastomer layer 40 which is in turn bondedto the reinforcing layer 41. The radial component of the load on thepacker retaining ring 21 is contained by hoop stress within theretaining ring 21. The axial component of the load on the retaining ring21 is transferred to the rigid sleeve 23 via the contact surface atlocation 44. The axial load imparted on the retaining ring 21 istransferred through shear stress in the elastomer layer 40 back to thereinforcing layer 41. The contact surface 44 is shown as an acute angledabutment so that the rigid sleeve 23 does not disengage under load fromthe packer retaining ring 21.

The inflation valve system which permits fluid to expand the packersleeve 4 is fitted in a concentric recess in the mandrel 5 at location48. Although one inflation valve 7 is illustrated, it is to beunderstood that a number of such valves are formed around the packermandrel 5. At the location 48, a port 47 is drilled in the mandrel 5 toprovide an inflation fluid entry point. Movement of the inflation valve7 is provided by an elastomeric annular flap 46 which is bonded over theoutside surface of the mandrel 5 at location 45. The bonding of theannular end of the elastomeric annular flap 46 to the mandrel 5 is underthe metal retaining ring 21 to maintain the annular edge of the flap 46anchored to the mandrel 5. During inflation of the packer sleeve 4, theinflation fluid forces the elastomeric annular flap 46 open, as shown inthe drawing. When pumping the packer inflation fluid to a specifiedpressure, the grout valves rupture and open, whereupon the pressure inthe casing drops, thereby causing the elastomeric annular flap 46 toclose the respective ports 47. The inflation valve 7 is held in theclosed state by fluid pressure contained between the packer sleeve 4 andthe mandrel 5. The force exerted on the inside of the closed elastomericannular flap 46 by the inflated packer sleeve 4 is greater than thefluid force exerted on the other side of the inflation flapper 46 by thecement grout forced down the casing during the grouting process.Accordingly, the cement grout does not force the flapper valve 46 openduring the grouting process. Otherwise, the cement grout would enterbetween the packer sleeve 4 and the mandrel 5.

The rigid outer sleeve 23 is advantageously made in longitudinally splitform so as to facilitate assembly of the packer while minimising theneed for precise tolerance in diameter between the rigid outer sleeve 23and the elastomer layer 40. During assembly, the rigid, split sleeve 23is clamped into place to the underlying elastomer layer 40 to permit theformation of a bond therebetween. It should be appreciated by thoseskilled in the art of elastomer construction that various bond andde-bonded sections of layers are advantageous to produce the ECP.

FIG. 6 illustrates the structural details of the lower end of the packersleeve 4 as shortened during inflation. The lower end of the packersleeve 4 includes the sliding seal 55, the retaining ring 20 and theouter sleeve layer 40. The arrangement of the packer sleeve 4 at thelower end thereof includes the inner elastomer layer 42, the reinforcinglayer 41, the outer elastomer layer 40, the retaining ring 20, and therigid outer sleeve 22, all of which are similar in construction to thatdescribed above in connection with the upper end of the packer in FIG.5. The major difference is that the inner elastomer layer 42 ismanufactured so that it can slide over the mandrel 5 in an axialdirection at surface area 53 as the packer sleeve 4 shortens duringinflation. Unlike most packers which have a form of sliding hydraulicseal, the packer disclosed herein utilises an annular sleeve seal 55made of an elastomer which is preferably of a similar elastomerconstruction as the sleeve 4. The annular sleeve seal 55 is contained inan annular external groove 54 formed in the mandrel 5. The annularsleeve seal 55 is bonded to the outside of the mandrel 5 over surfacearea 58, and to the inside of the packer inner elastomer layer 42 oversurface area 57. The sleeve seal 55 is otherwise not bonded, but is freeto slide axially on the mandrel 5 within the external groove 54. In thedrawing the packer sleeve 4 is shown in an inflated state, engaged incontact with the borehole 1. In the inflated state the sleeve seal 55 islongitudinally compressed from its original position where it occupiesthe entire length of the external groove 54. The distance by which thesleeve seal 55 becomes compressed is shown as the dimension G. Thesleeve seal 55 is shown in the drawing as having been manufactured witha reinforcing layer 56. This would preferably be an open weave mesh laidon the bias so that it can compress axially. The reinforcing mesh 56would be bonded into the elastomer and prevent uneven strain of thesleeve seal 55, which could otherwise lead to tears within the materialof the sleeve seal 55. The sleeve seal 55 is held against the mandrel 5within groove 54 by fluid pressure in the expanded sleeve 4 and isprevented from being torn from the inner elastomer 42 of the sleeve 4 bythe tight annular restraint of the packer retaining ring 20.

While, the preferred and other embodiments of the invention have beendisclosed with reference to a specific external casing packer, andassociated methods of use and manufacture thereof, it is to beunderstood that many changes in detail may be made as a matter ofengineering choices without departing from the spirit and scope of theinvention, as defined by the appended claims.

1. A method of cement grouting an annulus between a casing and aborehole using an inflatable packer system, comprising: placing a casingwith an external casing packer attached thereto at a location in aborehole for cement grouting a portion of the borehole annulus that islocated above the external casing packer; inflating an inflatableelastomeric sleeve of the external casing packer to block the annulus ofthe borehole by pressurising the casing with an inflation fluid, whichopens a one-way inflation valve in the external casing packer with thepressurised inflation fluid and inflates the inflatable sleeve to apreset pressure; determining the preset pressure by a pressure reliefvalve located between the external casing packer and the annulus whichopens at the preset pressure and then becomes a one-way grout valve;pumping a liquefied cement grout mixture down through the casing via theopen one-way grout valve which is located in the external casing packerabove a portion of the inflated inflatable sleeve; and biasing the groutvalve to a closed position using an elastomeric member attached to thepacker, whereby when the pressure of the cement grout mixture is reducedin the casing, the elastomeric member causes the grout valve to closeand prevent backflow of the cement grout mixture from the annulus backinto the casing.
 2. The method of claim 1, further including rupturingor shearing a portion of the grout valve at a given pressure to open thegrout valve and permit a pressure drop in the casing.
 3. The method ofclaim 2, further including using the pressure drop in the casing tomaintain closure of the sleeve inflation valve.
 4. The method of claim1, further including pressurising the casing to open the one-wayinflation valve and inflate the inflatable sleeve, and using thepressurised casing to shear an element of the grout valve to allow thegrout valve to open when the inflatable sleeve is inflated.
 5. Themethod of claim 1, further including biasing the grout valve to a closedcondition by the elastomeric member, by using an elastomeric sleevemember which both encircles the packer and is attached to a movable partof the grout valve.
 6. The method of claim 1, further includingfabricating the elastomeric sleeve of the grout valve as part of theinflatable elastomeric sleeve, whereby when the grout valve is openedthe elastomeric sleeve member stretches radially outwardly.
 7. Themethod of claim 5, further including bonding a portion of theelastomeric sleeve of the grout valve to a mandrel of the packer andbonding the elastomeric sleeve of the grout valve to a chamfered groutvalve member, which is the movable member of the grout valve.
 8. Themethod of claim 5, further including forming the elastomeric sleevemember as a unitary part of the inflatable elastomeric sleeve during onemanufacturing process.
 9. The method of claim 1, further including usinga sleeve of an elastomeric material as a flap member of the non-returninflation valve, and bonding one annular edge of the elastomeric flapmember sleeve to the mandrel of the packer, allowing another annularedge of the sleeve of elastomer material to be free for lifting off ofrespective ports in the mandrel to permit one-way fluid flow.
 10. Amethod of setting an external casing packer in an annulus of a boreholeto fix a casing therein, comprising: sealing a base of the packer;pressurising the packer to inflate an inflatable elastomeric sleevesurrounding a portion of a packer mandrel by passing a pressurised fluidthrough a one-way inflation valve into the inflatable sleeve; limitingthe inflation pressure of the inflatable sleeve by using a pressurerelief valve in the packer which relieves the pressure in the packer tothe outside of the casing when a design differential pressure isreached; using the pressure relief valve as a one-way valve to permit agrout material to flow therethrough to the annulus of the borehole; andclosing the pressure relief valve to prevent a backflow of the groutmaterial from the annulus back into the packer.
 11. A method accordingto claim 10 whereby the base of the packer is sealed by dropping a ballinto a seat located in the base of the packer.
 12. A method of cementgrouting a borehole using an inflatable packer system, comprising:lowering into a borehole a casing with the inflatable packer systemattached thereto; pressurising the casing with a fluid so that thepressurised fluid enters one or more one-way inflation valves in thepacker system to inflate a sleeve and obstruct an annulus of theborehole; increasing the pressure of the fluid in the casing until oneor more one-way frangible grout valves rupture to allow pressurisedfluid to enter the borehole annulus above the packer system, whereby thepressure of the casing drops and the one-way inflation valves close andmaintain the inflation of the sleeve in the borehole annulus; pumpingcement grout down through the casing and through the ruptured one-waygrout valves into the portion of the borehole annulus located above thepacker system.
 13. The method of claim 12, further including pumping apredetermined volume of the cement grout down the casing and into theborehole annulus, and then stopping the pumping of the cement grout,whereby the one-way grout valves close and prevent a backflow of thecement grout from the annulus back into the casing.
 14. The method ofclaim 12, further including sealing the base of the packer system beforepumping the cement grout down the casing to prevent the cement groutfrom passing into a perforated portion of the casing below the packersystem.
 15. The method of claim 13, further including forcing a plugdown through the casing after the predetermined volume of cement grouthas been pumped down the casing, to clear at least a portion of thecement gout from the casing and force the same through the one-way groutvalves and into the borehole annulus.
 16. The method of claim 15,further including drilling the portion of the cement grout that has setin the packer system to provide a flow path of production fluid from thebottom of the borehole to the top of the casing.
 17. The method of claim12, further including forming an elastomeric sleeve around a mandrelbody of the packer system, where an annular top portion of the sleeve isanchored and scaled to the mandrel, and a bottom portion of the sleeveis slideable along and sealed to the mandrel as the sleeve is inflated.18. The method of claim 17, further including forming a portion of theelastomeric sleeve over the one-way grout valves so that elasticity ofthe sleeve moves the one-way grout valves into closed positions inrespective ports formed in the mandrel.
 19. The method of claim 17,further including anchoring the top portion of the sleeve to the mandrelusing a retaining ring which clamps the sleeve around the mandrel, andforming the one-way inflation valves by using an elastomeric flapperwhich covers respective ports formed in the mandrel, where the flappersare anchored at one end thereof to the mandrel under the retaining ring.20. An inflatable packer system for grouting a borehole annulus, saidpacker system comprising: a mandrel forming a body of the packer system,said mandrel adapted for attachment to a casing, said mandrel havingformed therein one or more ports for respective grout valves, and one ormore ports for respective inflation valves; a seat formed in a bottompart of said mandrel, said seat adapted for being blocked by a balldropped down the easing; an elastomeric sleeve formed around the mandreland around the inflation valve ports; an anchor seal formed at a topportion of the elastomeric sleeve around the mandrel above the inflationvalve ports and below the grout valve ports; a sliding seal formed at abottom portion of the elastomeric sleeve along said mandrel; one or moreone-way inflation valves, each said one-way inflation valve located overone said inflation valve port, each said one-way inflation valve adaptedfor allowing an inflation fluid to pass through the inflation valve portand into the elastomeric sleeve, but not in a reverse direction; one ormore one-way grout valves, each said one-way grout valve located overone said grout valve port, each said one-way grout valve adapted forallowing a cement grout to pass through the grout valve port and intothe borehole annulus, but not in a reverse direction; and each saidone-way grout valve formed with a frangible member which breaks inresponse to a predetermined inflation fluid pressure, whereby when saidelastomeric sleeve is inflated to the predetermined fluid pressure thefrangible members break to enable operation of the one-way grout valves,and the one-way inflation valves close to allow the elastomeric sleeveto maintain the predetermined inflation fluid pressure.